Bi-directional packet data transmission system and method

ABSTRACT

A bi-directional packet data transmission system for a packet data transmission between a terminal and a radio access network includes an uplink resource and a downlink resource which are independently set. Memory resources can be effectively managed even in a packet data transmission service with the asymmetrical structure such that the packet amount for the downlink is much greater than the packet amount for the uplink, or the packet amount for the uplink is much greater than the packet amount for the downlink.

[0001] This application claims the benefit of the Korean Application No.P2002-48261 filed on Aug. 14, 2002, which is hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a packet data transmission and,more particularly, to a packet data transmission method and system of amobile communication system.

[0004] 2. Discussion of the Related Art

[0005] Recently, a mobile communication system has seen a remarkabledevelopment, but in terms of a large capacity data communicationservice, it is much behind the cable communication system. Countriesthroughout the world are developing a technique of IMT-2000 and activelycooperating for standardization of the technique.

[0006] A universal mobile telecommunications system (UMTS) is a thirdgeneration mobile communication system that has evolved from a standardknown as Global System for Mobile communications (GSM). This standard isa European standard which aims to provide an improved mobilecommunication service based on a GSM core network and wideband codedivision multiple access (W-CDMA) technology.

[0007] In December, 1998, the ETSI of Europe, the ARIB/TTC of Japan, theT1 of the United States, and the TTA of Korea formed a Third GenerationPartnership Project (3GPP) for the purpose of creating the specificationfor standardizing the UMTS.

[0008] The work toward standardizing the UMTS performed by the 3GPP hasresulted in the formation of five technical specification groups (TSG),each of which is directed to forming network elements having independentoperations.

[0009] More specifically, each TSG develops, approves and manages astandard specification in a related region. Among them, a radio accessnetwork (RAN) group (TSG-RAN) develops a specification for the function,items desired, and interface of a UMTS terrestrial radio access network(UTRAN), which is a new RAN for supporting a W-CDMA access technology inthe UMTS.

[0010]FIG. 1 illustrates an example of the construction of a generalUMTS network. As shown in FIG. 1, the UMTS is roughly divided into aterminal, UTRAN 100 and a core network 200.

[0011] The UTRAN 100 includes one or more radio network sub-systems(RNS) 110 and 120. Each RNS 110 and 120 includes a radio networkcontroller (RNC) 111 and plural Node Bs 112 and 113 managed by the RNC111. The RNC performs functions which include assigning and managingradio resources, and operates as an access point with respect to thecore network 200.

[0012] Node Bs 112 and 113 receive information sent by the physicallayer of the terminal through an uplink, and transmit data to theterminal through a downlink. The Node Bs 112 and 113, thus, operate asaccess points of the UTRAN for the terminal.

[0013] The core network 200 includes a mobile switching center (MSC) 210and a gateway mobile switching center (GMSC) 220 for supporting acircuit switched service, and a serving GPRS support node (SGSN) 230 anda gateway GPRS support node 240 for supporting a packet switchedservice.

[0014] The services provided to a specific terminal is roughly dividedinto the circuit switched service and the packet switched service. Forexample, a general voice phone call service belongs to the circuitswitched service, while a Web browsing service through an Internetconnection is classified as the packet switched service.

[0015] In case of supporting the circuit switched service, the RNC 111is connected to the MSC 210 of the core network 200, and the MSC 210 isconnected to the GMSC 220 managing a connection to other networks.

[0016] Meanwhile, in case of supporting the packet switched service, theRNC 111 provides a service in association with the SGSN 230 and the GGSN240 of the core network 200. The SGSN 230 supports a packetcommunication going toward the RNC 111, and the GGSN 240 managesconnection to other packet switched network such as the Internetnetwork.

[0017] Various interfaces exist between network components to allow thenetwork components to give and take information to and from each otherfor a mutual communication. An interface between the RNC 111 and thecore network 200 is defined as an Iu interface. Especially, an Ininterface between packet switch-related systems of the RNC 111 and thecore network 200 is defined as an Iu-PS, and an Iu interface betweencircuit switch-related systems of the RNC 111 and the core network 200is defined as an Iu-CS.

[0018]FIG. 2 illustrates a structure of a radio interface protocolbetween the terminal and UTRAN 100 according to the 3GPP radio accessnetwork standards.

[0019] As shown in FIG. 2, the radio interface protocol is verticallydivided into a physical layer, a data link layer and a network layer,and is horizontally divided into a user plane (U-plane) for transmittingdata signal and a control plane (C-plane) for transmitting a controlsignal.

[0020] The user plane is a region handling traffic information of a usersuch as a voice signal or an IP packet, while the control plane is aregion handling control information such as an interface of a network ormaintenance and management of a call.

[0021] In FIG. 2, protocol layers can be divided into a first layer(L1), a second layer (L2), and a third layer (L3) based on three lowerlayers of an open system interconnection (OSI) standard model.

[0022] Functions of each protocol layer of FIG. 2 will now be described.

[0023] The first layer (L1), that is, the physical layer, provides aninformation transfer service to a higher layer by using various radiotransfer techniques.

[0024] The physical layer is connected to the MAC layer, a higher layer,through a transport channel, and the MAC layer and the physical layertransfer signals through the transport channel.

[0025] The second layer (L2) includes: an MAC layer, a radio linkcontrol (RLC) layer and a packet data convergence protocol (PDCP) layer.

[0026] The MAC layer provides a re-allocation service of the MACparameter for allocation and re-allocation of radio resources.

[0027] The MAC layer is connected to the radio link control (RLC) layerthrough a logical channel, and various logical channels are providedaccording to the kind of transmitted information.

[0028] In general, when information of the control plane is transmitted,a control channel is used. When information of the user plane istransmitted, a traffic channel is used.

[0029] The RLC layer supports a reliable data transmission and performsfunctions of segmentation and reassembly of an RLC service data unit(SDU) received from an upper layer.

[0030] When the RLC SDU is received from the higher layer, the RLC layercontrols a size of each RLC SDU to be suitable to a process capacity,and adds header information thereto to generate a certain data unit. Thethusly generated data unit is referred to as a protocol data unit (PDU)which is transferred to the MAC layer. The RLC layer includes an RLCbuffer for storing the RLC SDU or the RLC PDU.

[0031] The packet data convergence protocol (PDCP) layer is a higherlayer of the RLC layer. A data transmitted through a network protocolsuch as an IPv4 (internet Protocol version 4) or an IPv6 (internetProtocol version 6) can be transmitted effectively on a radio interfacewith a relatively small band width by virtue of the PDCP layer.

[0032] For this purpose, the PDCP layer performs a function of reducingunnecessary control information used in the cable network, which iscalled a header compression, for which header compression schemes suchas an RFC2507 or an RFC3095 (Robust Header Compression (ROHC)) definedby an Internet standardization group called an IETF (InternetEngineering Task Force) are used.

[0033] In these schemes, only information requisite for a header part ofa data is transmitted, thereby reducing an amount of data to betransmitted. That is, unnecessary fields of the header are removed or asize of the header fields is reduced to reduce the amount of data of theheader part.

[0034] An RRC (Radio Resource Control) layer is positioned at the lowestportion of the third layer. The RRC layer is defined only in the controlplane and controls the transport channels and the physical channels inrelation to the setup, the reconfiguration and the release of the radiobearers (RBs).

[0035] The RB service signifies a service provided by the second layerfor data transmission between the terminal and UTRAN, and setting up ofthe RB means processes of stipulating the characteristics of a protocollayer and a channel, which are required for providing a specificservice, and setting the respective detailed parameters and operationmethods.

[0036] For reference, the RLC layer can be included in the user plane orin the control plane depending on which layer is connected at an upperposition. If the RLC layer receives data from the RRC layer, the RLClayer belongs to the control plane, and otherwise, the RLC layer belongsto the user plane.

[0037] As shown in FIG. 2, in case of the RLC layer and the PDCP layer,a plurality of entities can exist in one layer. This is because oneterminal has a plurality of RBs, and generally one RLC entity (or onlyone PDCP entity) is used for one RB.

[0038]FIG. 4 is a signal flow chart for implementing the headercompression scheme in accordance with a conventional art, and FIG. 5illustrates a structure of a compressor and decompressor of the terminaland UTRAN.

[0039] An IP header compression scheme of the PDCP layer will now bedescribed with reference to FIGS. 4 and 5.

[0040] First, referring to the RFC2507, different compression schemesare used depending on whether an upper protocol of the IP layer is TCPor not. That is, if an upper protocol of the IP layer is UDP, acompression scheme called ‘compressed non-TCP’ is used whereas if theupper protocol of the IP layer is TCP, a compression scheme called‘Compressed TCP’ is used. The Compressed TCP is classified into a‘Compressed TCP’ and a ‘Compressed TCP nodelta’ depending on atransmission method of a varied header field.

[0041] The ‘Compressed TCP’ scheme is a method that on the basis of thefact that variable header field values are not much different from eachother among successive packets, only a difference between header fieldsvalues is transmitted, rather than transmitting the overall field value.Meanwhile, the ‘Compressed TCP nodelta’ scheme is a method oftransmitting the overall varied field value as it is.

[0042] In the case of the ‘Compressed TCP’ scheme, a transmitting partyfirst transmits an overall header packet for one packet stream toconstitute a context both in the transmitting party and in a receivingparty, and then uses a compression header indicating the difference froma previous packet to transmit the next packets. Meanwhile, the‘Compressed TCP nodelta’ scheme is that the overall header field valueas varied is transmitted.

[0043] Likewise, in the ‘Compressed Non-TCP’ scheme, the transmittingparty first transmits an overall header packet for one packet stream toconstitute a context both in the transmitting party and the receivingparty, and transmits an overall header field value formed as a variablefield for the next packets.

[0044] However, the ‘Compressed Non-TCP’ header compression scheme canbe used for a uni-directional communication and adopts a compressionslow-start method which transmits overall header information atexponentially increasing intervals. In the compression slow-startmethod, if the overall header information is changed or if a new headercompression scheme is adopted, the same overall header is frequentlytransmitted at an initial stage and then a transmission interval isgradually widened. FIG. 3 shows a concept of the compression slow-startmethod.

[0045] Parameters constituting the forms of the compressor and thedecompressor should be defined to use the RFC2507 header compressionscheme at the PDCP layer.

[0046] Defined in the RFC2507 header compression scheme are anF_MAX_PERIOD parameter indicating the number of compressed Non-TCPheader packets transmittable between full header packets transmittedexponent-repeatedly in the compression slow-start method, an F_MAX_TIMEparameter indicating a compressed header packet transmission timebetween a time point when the latest full header packet has beentransmitted and a time point when the next full header packet is to betransmitted, an MAX_HEADER parameter indicating the maximum size of aheader usable for the header compression scheme, a TCP_SPACE parameterindicating the maximum number of contents usable for the ‘CompressedTCP’ scheme, a NON_TCP_SPACE parameter indicating the maximum number ofcontents used for the ‘Compressed Non-TCP’ scheme, and anEXPECTED_RECORDING parameter indicating whether re-sequential array issupported. The F_MAX_TIME parameter is used to inform a repetitionperiod of the full header packet (refer to FIG. 1).

[0047] The parameters are used to construct forms of the compressors 512and 522 and the decompressors 511 and 521 of the terminal 410 and UTRAN420 and defined in RFC2507, an IETF document of the RFC2507 headercompression scheme. TABLE 1 Information Element/Group name Type andreference Semantics description >>>F_MAX_PERIOD Integer (1 . . . 65535)Largest number of compressed non-TCP headers that may be sent withoutsending a full header. Default value is 256. >>>F_MAX_TIME Integer (1 .. . 255) Compressed headers may not be sent more than F_MAX_TIME secondsafter sending last full header. Default value is 5. >>>MAX_HEADERInteger (60 . . . 65535) The largest header size in octets that may becompressed. Default value is 168. >>>TCP_SPACE Integer (3 . . . 255)Maximum CID value for TCP connections. Default value is15. >>>NON_TCP_SPACE Integer (3 . . . 65535) Maximum CID value fornon-TCP connections. Default value is 15. >>>EXPECT_REORDERINGEnumerated Whether the algorithm shall reorder PDCP SDUs or not.(reordering not Default value is “reordering not expected”. expected,reordering expected)

[0048] The header compression and decompression process adopting theRFC2507 header compression scheme will now be described.

[0049] First, the RRC layer 411 of the terminal 10 transfers capacityinformation to the RRC layer 421 of UTRAN 420. Then, the RRC layer 421of UTRAN 420 allocates a memory resource required for header compressionby referring to the capacity information. That is, the RRC layer 421sets parameter values forming the compressors 512 and 522 and thedecompressors 511 and 521.

[0050] For example, F_MAX_PERIOD is set to 256, F_MAX_TIME is set to 5,MAX_HEADER is set to 168, and NON_TCP_SPACE is set to 15.

[0051] When the parameter values are all set, the RRC layer 421 of UTRAN420 transfers the set parameter values to the RRC layer 411 of theterminal 410.

[0052] As the parameter values reach the terminal 410, the RRC layer 411of the terminal 410 and the RRC layer 421 of UTRAN 420 respectivelytransfer the set parameter values to respective PDCP layers 412 and 422.Then, a header compression performing layer included in the PDCP layers412 and 422 forms the compressors 512 and 522 and the decompressors 511and 521 on the basis of the received parameter values.

[0053] The ROHC (Robust Header Compression) scheme will now bedescribed.

[0054] The ROHC scheme is commonly used to reduce header information ofan RTP (Real-time Transport Protocol)/UDP (User Datagram Protocol)/IP(Internet Protocol) packet. The RTP/UDP/IP packet, which means a packetwith RTP, UDP and IP related headers which have been added to a userdata while passing each layer, includes various header informationrequired for transmitting data to a destination through the Internet.

[0055] The ROHC scheme is a header compression scheme based on the factthat each field value of packet headers of sequential packets belongingto one packet stream is almost the same. Thus, in the ROHC scheme, notthe entire packet header field is transmitted but a variable field istransmitted.

[0056] For reference, an overall size of the header of the RTP/UDP/IPpacket is 40 octet in case of IPv4 (Internet Protocol version 4) and 60octet in case of IPv6 (internet Protocol version 6). Meanwhile, a puredata part (payload) usually has a size of 15˜20 octet. That is, becausethe amount of control information is much greater than the amount ofdata to be actually transmitted, a transmission efficiency is quite low.Therefore, using the header compression schemes ensures a hightransmission efficiency because the amount of control information ismuch reduced (in case of using the ROHC scheme, the size of the headeris reduced by about 1 octet to 3 octet).

[0057] Like the RFC2507 header compression scheme, in order to use theROHC scheme at the PDCP layer, parameters constituting the form of thecompressor and the decompressor should be defined.

[0058] Parameters defined for the ROHC scheme includes a Max_CIDparameter informing of the maximum number of contexts usable in thecompressor, a profile parameter indicating what is the type of the IPpacket used for a corresponding packet stream among RTP/UDP/IP, UDP/IPand ESP/IP, an MRRU (Maximum Reconstructed Reception Unit) parameterindicating whether an IP should be segmented and also indicating themaximum size of segments when they are reassembled after being segmentedin the decompressor, a Packet_Sized_Allowed parameter informing of asize of a compression header packet supportable by the ROHC scheme, anda Reverse_Decompression_Depth parameter indicating whether a compressedpacket has been re-attempted for decompression after the decompressorhad failed to decompress it, and determining the number of re-attemptsof decompression. These parameters are defined in the RFC3095, the IETFdocument of the ROHC scheme.

[0059] The header compression and decompression process adopting theROHC scheme is the same as those of the RFC2507 header compressionscheme as described above (refer to FIGS. 4 and 5).

[0060] For a communication to an uplink, the compressor 512 of theterminal 410 and the decompressor 521 of UTRAN 420 should have the sameform, and for a communication to a downlink, the compressor 522 of UTRAN420 and the decompressor 511 of the terminal 410 also should have thesame form.

[0061] Because, the RRC layer 421 of UTRAN 420 sets the parameter valuesto form the compressor and the decompressor without discrimination ofthe uplink and the downlink, the compressors 512 and 522 and thedecompressors 511 and 521 provided in the terminal 410 and UTRAN 420have all the same forms.

[0062] In order to effectively provide a VoIP service and a streamingservice and prevent consumption of radio resources, the UMTS systemadopts the header compression scheme such as the RFC2507 headercompression scheme or the ROHC scheme to compress a header from theoriginal size of 40 bytes or 60 bytes to a size of 1˜4 bytes andtransmit it. For this purpose, the terminal 410 and UTRAN 420 shoulddefine parameters for forming the compressor and the decompressor.

[0063] Usually, the UMTS system also provides the streaming service inwhich the uplink and the downlink are asymmetrical as well as the VoIPservice in which the uplink and the downlink are symmetrical.

[0064] In this respect, however, the RRC layers 411 and 421 and the PDCPlayers 412 and 422 sets a memory resource in consideration of only thetransmission service in the uplink and downlink-symmetrical structuresuch as the VoIP (Voice over IP), so that the compressor anddecompressor 512 and 521 of the uplink and the compressor and thedecompressor 522 and 511 of the downlink have the same forms.

[0065] A problem of the conventional bi-directional packet datatransmission system lies in that, the UMTS system allocates the sameheader compression-related memory resource to the uplink and thedownlink even for the packet data transmission of the asymmetricalstructure such as the streaming service.

[0066] The streaming service is a downlink-oriented service in which apacket data for a service requested by a user is transmitted through thedownlink while reception information for the transmitted packet data isfed back through the uplink.

[0067] In terms of characteristics of the streaming service, the amountof the packet data transmitted to the downlink is much greater than theamount of packet data transmitted to the uplink. Thus, the conventionalbi-directional packet data transmission system is disadvantageous thatthe memory resources used for the header compression scheme areunnecessarily wasted and thus efficiency of the resources is degraded.

[0068] The above references are incorporated by reference herein whereappropriate for appropriate teachings of additional or alternativedetails, features and/or technical background.

SUMMARY OF THE INVENTION

[0069] Accordingly, the present invention is directed to a bidirectionalpacket data transmission system and method that substantially obviatesone or more problems due to limitations and disadvantages of the relatedart.

[0070] An advantage of the present invention is a bi-directional packetdata transmission system and method capable of asymmetrically setting anuplink memory resource and a downlink memory resource.

[0071] Additional advantages and features of the invention will be setforth in part in the description which follows and in part will becomeapparent to those having ordinary skill in the art upon examination ofthe following or may be learned from practice of the invention. Theseand other advantages of the invention may be realized and attained bythe structure particularly pointed out in the written description andclaims hereof, as well as the appended drawings.

[0072] To achieve these and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein,there is provided a bi-directional packet data transmission system for apacket data transmission between a terminal and a radio access network,in which an uplink resource and a downlink resource are independentlyset.

[0073] Preferably, the resource is a memory resource.

[0074] Preferably, the memory resource is related to header compression.

[0075] Preferably, the memory resource has parameters required forheader compression and decompression.

[0076] Preferably, an RRC layer of the radio access network setsresources to be different for uplink transmission and downlinktransmission.

[0077] Preferably, a PDCP layer of the terminal forms a compressor byreferring to received parameter values of the uplink and a decompressorby referring to received parameter values of downlink, and performsheader compression and decompression.

[0078] Preferably, a PDCP layer of the radio access network forms adecompressor by referring to received parameter values of the uplink anda compressor by referring to received parameter values of downlink, andperforms header compression and decompression.

[0079] In another aspect of the present invention, there is furtherprovided a bi-directional packet data transmission system for a packetdata transmission between a terminal and a radio access network,including: setting an uplink resource and a downlink resource to bedifferent; transferring the set resource to each PDCP layer of aterminal and a radio access network; and asymmetrically performinguplink and downlink transmission by using the received resource.

[0080] Preferably, in the resource setting step, parameters required forheader compression and decompression are determined and sizes of theparameters are set.

[0081] Preferably, the asymmetrical transmission performing stepincludes: forming a compressor by referring to the received parametervalues of uplink and a decompressor by referring to the receivedparameter values of downlink; and performing a packet transmissionaccording to a header compression scheme by using the compressor and thedecompressor.

[0082] Preferably, the asymmetrical transmission performing stepincludes: forming a decompressor by referring to the received parametervalues of uplink and a compressor by referring to the received parametervalues of downlink; and performing a packet transmission according to aheader compression scheme by using the compressor and the decompressor.

[0083] It is to be understood that both the foregoing generaldescription and the following detailed description of the presentinvention are exemplary and explanatory and are intended to providefurther explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this application, illustrate embodiment(s) of theinvention and together with the description serve to explain theprinciple of the invention.

[0085] In the drawings:

[0086]FIG. 1 illustrates a construction of a general UMTS network;

[0087]FIG. 2 illustrates a structure of a radio interface protocolbetween a terminal and UTRAN on the basis of 3GPP radio access networkstandards;

[0088]FIG. 3 illustrates a concept of a compression slow-start scheme;

[0089]FIG. 4 is a signal flow chart for implementing a headercompression scheme in accordance with a conventional art;

[0090]FIG. 5 illustrates structures of compressors and decompressors ofa terminal and UTRAN in accordance with the conventional art;

[0091]FIG. 6 is a signal flow chart for implementing a headercompression scheme in accordance with a preferred embodiment of thepresent invention; and

[0092]FIG. 7 illustrates structures of compressors and decompressors ofa terminal and UTRAN in accordance with the preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0093] Reference will now be made in detail to embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

[0094]FIG. 7 illustrates structures of compressors and decompressors ofa terminal or mobile unit and UTRAN in accordance with the preferredembodiment of the present invention and shows transmission in anasymmetrical structure between an uplink and a downlink.

[0095] As shown in FIG. 7, a compressor and a decompressor of thepresent invention have the same structures as those of the conventionalart (refer to FIG. 5).

[0096] The only difference of the present invention from theconventional art is that UTRAN 620 and a terminal 610 allocate a memoryresource required for a header compression scheme to the uplink and thedownlink in consideration of transmission that the uplink and downlinkare asymmetrical as well as the transmission that uplink and downlinkare symmetrical.

[0097]FIG. 6 is a signal flow chart for implementing a headercompression scheme in accordance with a preferred embodiment of thepresent invention.

[0098] As shown in FIG. 6, a bi-directional packet data transmissionsystem in accordance with a preferred embodiment of the presentinvention includes: UTRAN 620 for setting header compression-relatedparameter values required for uplink transmission and downlinktransmission, and forming a compressor 722 and a decompressor 721; and aterminal 610 for transmitting the capacity information to UTRAN 620,receiving the set header compression-related parameter values from UTRAN620 and forming a compressor 712 and a decompressor 711 by referring tothe received parameter values.

[0099] UTRAN 620 includes an RRC layer 621 for setting the headercompression-related parameter values required for uplink transmissionand downlink transmission and transmitting the parameter values to anRRC layer 611 of the terminal and to its PDCP layer (622); and the PDCPlayer 622 for forming the decompressor 721 used for uplink transmissionand the compressor 722 used for downlink transmission, and performing aheader compression and decompression.

[0100] The terminal 610 includes the RRC layer 611 for receiving theparameter values set by the RRC layer 621 of UTRAN 620 and transmittingthe values to its PDCP layer 612; the PDCP layer 621 for forming thecompressor 712 used for uplink transmission and the decompressor 711used for downlink transmission by referring to the received parametervalues, and performing header compression and decompression; and a firstand second memory spaces for the uplink and downlink data transmissions,respectively. The two memory spaces may be independent of each other.

[0101] The operation of the packet data transmission system will now bedescribed.

[0102] To begin with, the RRC layer 611 of the terminal 610 transfersthe ‘capacity information’ to the RRC layer 621 of UTRAN 620.

[0103] Then, the RRC layer 621 of UTRAN 620 discriminates capacityinformation of uplink and capacity information of downlink from thereceived capacity information. Subsequently, the RRC layer setsparameter values for forming the compressor 712 and the decompressor 721of the uplink by referring the uplink capacity information and also setsparameter values for forming the compressor 722 and the decompressor 711of downlink by referring to the downlink capacity information.

[0104] The parameter values are not necessarily set on the basis ofcapacity information of the terminal. They can be set according to astatistical calculation value previously set in UTRAN 620.

[0105] After the parameter values are completely set, the RRC layer 621of UTRAN 620 transfers the set parameter values to the RRC layer 611 ofthe terminal 610. The RCC layer 621 can transfer the set parameters foreither the compressor only (uplink), the decompressor only (downlink),or both.

[0106] As the set parameter values transferred to the terminal 610, theRRC layer 611 of the terminal 610 and the RRC layer of UTRAN 620transfers the set parameter values to the PDCP layers 612 and 622. Then,each header compression performing layer included in the PDCP layers 612and 622 forms the compressors 712 and 722 and the decompressors 711 and721 by referring to the parameter values.

[0107] Specifically, the header compression performing layer of UTRAN620 forms the decompressor 721 used for uplink transmission and thecompressor 722 used for downlink transmission by referring to theparameter values, and the header compression performing layer of theterminal 610 forms the compressor 712 used for uplink transmission andthe decompressor 711 used for downlink transmission by referring to theparameter values.

[0108] And then, the header compression performing layers of theterminal 610 and UTRAN 620 perform header compression and decompressionaccording to a certain header compression scheme by using thecompressors 712 and 722 and the decompressors 711 and 721.

[0109] As described above, in the bi-directional packet datatransmission system in accordance with the preferred embodiment of thepresent invention, the compressor 712 and the decompressor 711 of theterminal 610 (or the form of the compressor 722 and the decompressor 721of UTRAN 620) are constructed in a different form so that the headercompression-related memory resources allocated to the uplink and thedownlink are set different. The forms of the compressor and thedecompressors 712, 721, 722 and 711 which have peer-to-peer relationsare the same with each other.

[0110] The bi-directional packet data transmission system in accordancewith the present invention performs the header compression anddecompression by adopting the RFC2507 header compression scheme or theROHC scheme.

[0111] First, in the case of adopting the RFC2507 header compressionscheme for the bi-directional packet data transmission system, thecompressor 712 of the terminal 610 performing the uplink communicationand the decompressor 721 of UTRAN 620 are formed by an F_MAX_PERIODparameter informing of a transmission period of an full header packetwith respect to the compression slow-start scheme, an F_MAX_TIMEparameter informing of packet transmission available time, a MAX_HEADERparameter informing of the maximum compressible size of a header, aTCP_SPACE parameter informing of the maximum size of a TCP packetcontext, and a NON_TCP_SPACE parameter informing of the maximum size ofnon-TCP packet context.

[0112] The compressor 722 of UTRAN performing the downlink communicationand the decompressor 711 of the terminal 610 are formed by a TCP_SPACEparameter informing of the maximum size of TCP packet context, a NON_TCPSPACE parameter informing of the maximum size of the non-TCP packetcontext, and an EXPECTED_REORDERING parameter informing of are-sequential array of a reception packet.

[0113] Second, in the case of adopting the ROHC scheme for thebi-directional packet data transmission system, the compressor 712 ofthe terminal 610 performing the uplink communication and thedecompressor 721 of UTRAN 620 are formed by a Max_CID parameterinforming of the maximum number of contexts used for the headercompression scheme, a profile parameter informing of a kind of an IPpacket supportable by the decompressor, an MRRU parameter informingwhether an IP packet can be segmented in the compressor, and aPacket_Sized_Allowed parameter determining sizes of compression headerpackets usable in the compressor.

[0114] In addition, the compressor 722 of UTRAN 620 performing thedownlink communication and the decompressor 711 of the terminal 610 areformed by a Max_CID parameter informing of the maximum number ofcontexts, a profile parameter informing of a kind of an IP packetsupported by the decompressor, an MRRU parameter informing of themaximum size of added packets when divided segments are added in thedecompressor, and a Reverse_Decompression_Depth parameter informing ofthe maximum storage size of a buffer which stores a decompression-failedpacket.

[0115] As so far described, the packet data transmission method andsystem of the present invention has the following advantages.

[0116] That is, because the memory resources are set to be different forthe uplink and downlink transmission, waste of the memory resource canbe prevented. In addition, the memory resource can be effectivelymanaged even in a packet data transmission service (e.g., the streamingservice) with the asymmetrical structure that the packet amount of thedownlink is much greater than the packet amount of the uplink, or thepacket amount of the uplink is much greater than the packet amount ofthe downlink.

[0117] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present invention. Thus,it is intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A data transmission system using packet datahaving a header, comprising: a radio access network having a firstheader compressor and a first header decompressor, the radio accessnetwork determining header compression parameter information, whereinthe header compression parameter information is separately configuredfor uplink and downlink data transmissions; and a mobile unit having asecond header compressor and a second header decompressor, the mobileunit receiving the header compression parameter information, wherein themobile unit has a first memory space allocation for the uplink datatransmission and a second memory space allocation for the downlink datatransmission, the first and second memory space allocations beingindependent from each other; wherein the radio access network and themobile unit operate under an internet protocol.
 2. The data transmissionsystem according to claim 1, wherein the radio access network determinesthe header compression parameter information using information from themobile unit, wherein the information includes mobile unit capability. 3.The data transmission system according to claim 2, wherein theinformation includes memory space.
 4. The data transmission systemaccording to claim 2, wherein the information includes a headercompression scheme.
 5. The data transmission system according to claim4, wherein the header compression scheme is a RFC3095 compressionscheme.
 6. The data transmission system according to claim 4, whereinthe header compression scheme is a RFC2507 compression scheme.
 7. Thedata transmission system according to claim 2, wherein the informationincludes a header compression scheme and memory space.
 8. The datatransmission system according to claim 7, wherein the header compressionscheme is a RFC3095 compression scheme.
 9. The data transmission systemaccording to claim 7, wherein the header compression scheme is a RFC2507compression scheme.
 10. The data transmission system according to claim1, wherein the radio access network sends the header compressionparameter information for both the uplink and downlink datatransmissions.
 11. The data transmission system according to claim 1,wherein the radio access network sends the header compression parameterinformation for only downlink data transmission.
 12. The datatransmission system according to claim 1, wherein the radio accessnetwork sends the header compression parameter information for only theuplink data transmission.
 13. The data transmission system according toclaim 1, wherein the header compression parameter information includesheader compression parameter values set corresponding to the uplink anddownlink data transmissions.
 14. The data transmission system accordingto claim 13, wherein a packet amount of the downlink transmission isgreater than a packet amount of the uplink transmission.
 15. The datatransmission system according to claim 13, wherein a packet amount ofthe downlink transmission is less than a packet amount of the uplinktransmission.
 16. The data transmission system according to claim 1,wherein the header is compressed according to a RFC2507 headercompression scheme.
 17. The data transmission system according to claim1, wherein the header is compressed according to a RFC3095 headercompression scheme.
 18. A method of communicating between a radio accessnetwork and a terminal of a data transmission system, comprising:transmitting capacity information to the radio access network;discriminating uplink information and downlink information from thecapacity information; setting parameter values for an uplink byreferring to the uplink information; setting parameter values for adownlink by referring to the downlink information; forming a firstcompressor according to the parameter values for the downlink; forming afirst decompressor according to the parameter values for the uplink;transferring the parameter values for the uplink from the terminal;transferring the parameter values for the downlink to the terminal;forming a second compressor according to the parameter values for theuplink; and forming a second decompressor according to the parametervalues for the downlink; wherein the parameter values for the uplink andthe parameter values for the downlink are different.
 19. The methodaccording to claim 18, wherein the uplink information and downlinkinformation include memory space information.
 20. The method accordingto claim 18, wherein the uplink information and downlink informationinclude a header compression scheme.
 21. The method according to claim20, wherein the header compression scheme is a RFC3095 compressionscheme.
 22. The method according to claim 20, wherein the headercompression scheme is a RFC2507 compression scheme.
 23. The methodaccording to claim 18, wherein the uplink information and downlinkinformation include memory space information and a header compressionscheme.
 24. The method according to claim 23, wherein the headercompression scheme is a RFC3095 compression scheme.
 25. The methodaccording to claim 23, wherein the header compression scheme is aRFC2507 compression scheme.
 26. A method of communicating between aradio access network and a terminal of a data transmission system,comprising: transmitting capacity information to the radio accessnetwork; discriminating uplink information from the capacityinformation; setting parameter values for only an uplink by referring tothe uplink information; forming a decompressor according to theparameter values for only the uplink; transferring the parameter valuesfor only the uplink from the terminal; and forming a compressoraccording to the parameter values for the uplink.
 27. The methodaccording to claim 26, wherein the uplink information includes memoryspace information.
 28. The method according to claim 26, wherein theuplink information includes a header compression scheme.
 29. The methodaccording to claim 28, wherein in the header compression scheme is aRFC3095 compression scheme.
 30. The method according to claim 28,wherein the header compression scheme is a RFC2507 compression scheme.31. The method according to claim 26, wherein the uplink informationincludes memory space information and a header compression scheme. 32.The method according to claim 31, wherein in the header compressionscheme is a RFC3095 compression scheme.
 33. The method according toclaim 31, wherein the header compression scheme is a RFC2507 compressionscheme.
 34. A method communicating between a radio access network and aterminal in a data transmission system, comprising: transmittingcapacity information to the radio access network; discriminatingdownlink information from the capacity information; setting parametervalues for only a downlink by referring to the downlink information;forming a compressor according to the parameter values for only thedownlink; transferring the parameter values for only the downlink to theterminal; and forming a decompressor according to the parameter valuesfor the downlink.
 35. The method according to claim 34, wherein thedownlink information includes memory space information.
 36. The methodaccording to claim 34, wherein the downlink information includes aheader compression scheme.
 37. The method according to claim 36, whereinin the header compression scheme is a RFC3095 compression scheme. 38.The method according to claim 36, wherein the header compression schemeis a RFC2507 compression scheme.
 39. The method according to claim 34,wherein the downlink information includes memory space information and aheader compression scheme.
 40. The method according to claim 39, whereinin the header compression scheme is a RFC3095 compression scheme. 41.The method according to claim 39, wherein the header compression schemeis a RFC2507 compression scheme.
 42. A method for communicating betweena terminal and a radio access network of a data transmission system,comprising: transmitting capacity information to the radio accessnetwork; receiving compression parameters from the radio access network;receiving decompression parameters from the radio access network;forming a compressor according to the received compression parameters;and forming a decompressor according to the received decompressionparameters; wherein the compression parameters are different from thedecompression parameters.
 43. The method according to claim 42, whereinthe capacity information comprises uplink information and downlinkinformation.
 44. A method of communicating between a radio accessnetwork and a terminal in a data transmission system, comprising:receiving capacity information from the terminal; discriminating uplinkinformation and downlink information from the received capacityinformation; setting parameter values for an uplink by referring to theuplink information; setting parameter values for a downlink by referringto the downlink information; forming a compressor according to theparameter values for the downlink; forming a decompressor according tothe parameter values for the uplink; transferring the parameter valuesfor the uplink to the terminal; and transferring the parameter valuesfor the downlink to the terminal; wherein the parameter values for thedownlink and the parameter values for the uplink are different.
 45. Themethod of claim 44, wherein the parameter values for the downlink andthe parameter values for the uplink are set according to a statisticalcalculation previously set in the radio access network.
 46. A method ofcommunicating between a radio access network and a terminal in a datatransmission system, comprising: receiving capacity information from theterminal; discriminating uplink information from the received capacityinformation; setting parameter values for an uplink only by referring tothe uplink information; forming a decompressor according to theparameter values for the uplink; and transferring the parameter valuesfor the uplink.
 47. The method of claim 46, wherein the parameter valuesare set according to a statistical calculation previously set in theradio access network.
 48. A method of communicating between a radioaccess network and a terminal in a data transmission system, comprising:receiving capacity information from the terminal; discriminatingdownlink information from the received capacity information; settingparameter values for a downlink only by referring to the downlinkinformation; forming a compressor according to the parameter values forthe downlink; and transferring the parameter values for the downlink.49. The method of claim 48, wherein the parameter values are setaccording to a statistical calculation previously set in the radioaccess network.
 50. A method of communicating between a radio accessnetwork and a terminal using packet data having a header, the methodcomprising: determining header compression parameter information by theradio access network having a first header compressor and a first headerdecompressor, the header compression parameter information beingseparately configured for uplink and downlink data transmissions; andtransmitting to a terminal having a second header compressor and asecond header decompressor the header compression parameter information,the terminal having a first memory space allocation for the uplink datatransmission and a second memory space allocation for the downlink datatransmission, the first and second memory space allocations beingindependent from each other; and operating the radio access networkunder an internet protocol.
 51. The method according to claim 50,wherein the radio access network sends the header compression parameterinformation for both the uplink and downlink data transmissions.
 52. Themethod according to claim 50, wherein the radio access network sends theheader compression parameter information for only downlink datatransmission.
 53. The method according to claim 50, wherein the radioaccess network sends the header compression parameter information foronly the uplink data transmission.
 54. The method according to claim 50,wherein the header compression parameter information includes headercompression parameter values set corresponding to the uplink anddownlink data transmissions.
 55. A method of communicating between aradio access network and a terminal using packet data having a header,the radio access network having a first header compressor and a firstheader decompressor, the method comprising: receiving by the terminalheader compression parameter information from the radio access network,the terminal having a second header compressor and a second headerdecompressor, the terminal having a first memory space allocation forthe uplink data transmission and a second memory space allocation forthe downlink data transmission, the first and second memory spaceallocations being independent from each other; operating the terminalunder an internet protocol.
 56. The method according to claim 55,wherein the terminal receives the header compression parameterinformation for both the uplink and downlink data transmissions.
 57. Themethod according to claim 55, wherein the terminal receives the headercompression parameter information for only downlink data transmission.58. The method according to claim 55, wherein the terminal receives theheader compression parameter information for only the uplink datatransmission.
 59. The method according to claim 55, wherein the headercompression parameter information includes header compression parametervalues set corresponding to the uplink and downlink data transmissions.